The present invention concerns new substituted 2,4-diaminophenols, processes for their preparation, and hair coloring agents containing such compounds.
So-called oxidative dyes are used extensively to color keratinic fibers because they produce intense dyes of high stability (fastness). Under the conditions of technical application (e.g., low dyeing temperature and short duration of dyeing) they yield intense colors with good stabilities. The dyes are formed in the dyeing process by oxidative coupling of a developer component and a coupler component. Such coupler and developer components for producing quite varied color tones, called hair dye intermediates in the following, are described often in the literature (K. Venkataraman, The Chemistry of Synthetic Dyes, Vol. V, Academic Press, 1971; F. Brody and M. S. Burns, J. Soc. Cosmet. Chem. (1968), volume 19, pages 361-379; H. Husemeyer, J. Soc. Cosmet. Chem. (1974), volume 25, pages 131-138).
Although the oxidative coupling, i.e., the development of the color, can in principle be done with oxygen from the air, in practice it usually goes too slowly or produces uneven colors. As a rule, then, chemical oxidizing agents are used. Oxidizing agents based on hydrogen peroxide are preferred. Along with hydrogen peroxide itself, addition compounds with urea, melamine or alkali perborate are also used.
For practical application as hair dyes, the hair dye intermediates are processed into a suitable cosmetic base which can, depending on the nature of the end product desired, be a solution, a cream, a foam (mousse) or a gel. This preparation is mixed with the oxidizing agent immediately before application to the hair.
As noted above, the oxidizing agent for color development can in principal also be oxygen from the air. However, experience teaches that the duration of color development or the temperatures required to shorten that time are too high for cosmetic use. No commercial product which comprises oxidation catalysts is known to the inventors.
Now it has been found, surprisingly, that such a hair coloring agent can be produced, in which, based on the usual foundation, the color-producing components are new substituted 2,4-diaminophenols of the general formula (I) or known couplers which react too slowly for air oxidation, which provide useful hair dyes through air oxidation on the hair by addition of a catalyst to the coloring material.